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排序方式: 共有609条查询结果,搜索用时 15 毫秒
601.
Fleming GR 《The journal of physical chemistry. A》2011,115(16):3607-3611
602.
Reinaldo G. Sotomayor Andrés R. Holguín Asma Romdhani Fleming Martínez Abolghasem Jouyban 《Journal of solution chemistry》2013,42(2):358-371
The solubility of piroxicam (PIR) in several ethanol + water mixtures was determined at five temperatures from 293.15 to 313.15 K. The thermodynamic functions; Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data and the drug properties of fusion by using the van’t Hoff and Gibbs equations. The greatest solubility value was obtained in pure ethanol. A non-linear enthalpy–entropy relationship was observed from a plot of enthalpy versus Gibbs energy of solution. Accordingly, the driving mechanism for PIR solubility in water-rich mixtures is the entropy, probably due to water-structure loss around the drug’s non-polar moieties by ethanol, whereas, in ethanol-rich mixtures the driving mechanism is the enthalpy, probably due to better PIR solvation by the co-solvent molecules. The solubilities and the derived thermodynamic properties in mixed solvents were correlated using the Jouyban–Acree model. 相似文献
603.
Dinesh Nath Prof. Fraser F. Fleming 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(6):2023-2029
Adding organolithiums, Grignard reagents, or zincates to sulfinylnitriles triggers a facile sulfinyl–metal exchange to afford N‐ or C‐metalated nitriles. Sulfinyl–magnesium exchange–alkylations efficiently install quaternary and tertiary centers, even in the case of tertiary sulfinylnitriles that contain a highly acidic methine proton. α‐Sulfinylalkenenitriles afford moderately nucleophilic magnesiated nitriles, and the reactivity can be dramatically increased by conversion to the corresponding magnesiates. The sulfinyl‐metal exchange is extremely fast, proceeds efficiently with quaternary, tertiary, and vinylic α‐sulfinylnitriles, and exhibits an exceptional functional group tolerance in nitrile alkylations. 相似文献
604.
Fleming AM Kannan A Muller JG Liao Y Burrows CJ 《The Journal of organic chemistry》2011,76(19):7953-7963
Exposure of cells to phenolic compounds through exogenous and endogenous sources can lead to deleterious effects via nucleobase modifications of DNA occurring under oxidative conditions. 2'-Deoxyguanosine (dG) is the most electron rich of the four canonical bases and includes many nucleophilic sites; it is also susceptible to oxidation with numerous reactive oxygen species. In these studies, dG was allowed to react with 2-naphthol in the presence of copper or iron salts yielding two principal isomeric products. Spectroscopic analysis and reactions with alkylated nucleosides support the assignment of compound 1a/1b as a pair of atropisomer N(2) adducts and compound 2a/2b as a diastereomeric mixture of tricyclic [4.3.3.0] adducts. Both products are the result of an overall four-electron oxidation process and consequently have the same masses, though drastically different structures, providing mechanistic insight into their formation. Thus, dG alkylation by 2-naphthol under oxidative conditions yields products whose structural properties are altered, leading to potentially mutagenic effects in genomic DNA. 相似文献
605.
The thermal poling method was utilized to create second-order optical nonlinearity in Pyrex borosilicate glass. The distribution and amplitude of the induced nonlinearity were characterized with second harmonic microscopy. The induced optical nonlinearity was found in a thin layer around 1.9 μm under the anode surface with a magnitude as high as 0.24 pm/V, comparable to that observed in fused silica samples. SEM observation of the cross-section of the poled glass region, after it had been etched in diluted hydrofluoric acid for several minutes, revealed an etched trench, ∼1.8 μm under the anode edge and ∼0.3 μm in width; while in post-annealed samples, no such etched trench could be observed. The effect of poling voltage on the magnitude of the induced nonlinearity was also studied, where the results showed that higher poling voltage resulted in higher nonlinearity with a threshold of ∼0.9 kV. 相似文献
606.
Aguilar-Arevalo AA Bazarko AO Brice SJ Brown BC Bugel L Cao J Coney L Conrad JM Cox DC Curioni A Djurcic Z Finley DA Fleming BT Ford R Garcia FG Garvey GT Green C Green JA Hart TL Hawker E Imlay R Johnson RA Kasper P Katori T Kobilarcik T Kourbanis I Koutsoliotas S Laird EM Link JM Liu Y Liu Y Louis WC Mahn KB Marsh W Martin PS McGregor G Metcalf W Meyers PD Mills F Mills GB Monroe J Moore CD Nelson RH Nienaber P Ouedraogo S Patterson RB Perevalov D Polly CC Prebys E Raaf JL Ray H Roe BP 《Physical review letters》2008,100(3):032301
607.
608.
The statistical and phenomenological theories of rubber elasticity are reviewed briefly. Combining recent concepts proposed by Yeoh and Gent, a new theory is proposed. The proposed constitutive model for rubber vulcanizates invokes two mechanisms; one influences behavior at small strains while the other dominates behavior at large strains. Network flaws, such as entanglements, are suspected to be responsible for the first mechanism. Finite extensibility of network chains is identified as the cause of the second. Thus, macroscopic behavior is directly linked to molecular concepts. The proposed theory allows prediction of the stress–strain behavior of a family of four rubber vulcanizates in different modes of deformation (simple extension, compression, and simple shear) from regression analysis of tensile data alone from just one member. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1919–1931, 1997 相似文献
609.